This invention relates to a continuous manufacturing process for sections or plates, and more particularly for corner bars. The invention also concerns and installation to implement the process and, needless to say, the products manufactured using said process.
For the manufacture of corner bars, strips of paper or cardboard are known to be glued together and covered with a casing that is preferably impermeable.
Also, paper-polythene complexes are known to be glued together under a flame and subsequently encased or not.
Products entirely in plastic material also exist. However, French patent 2 528 350 filed by the same holder, suggests in interesting manner that sections and plates can be made from a soft material which is extruded under heat and encased in at least one strip sheet, which unit is subsequently calendered, shaped to the desired profile and finally cut into lengths.
The material used is a thermoplastic material which may or may not contain other materials, and the process described in the above-mentioned patent is chiefly innovative compared with some other processes using thermoplastic, in that it avoids plastic flow or the thermoplastic material by fully encasing the material with one or two strip sheets taking care that the edges are properly covered.
The invention sets forth a process of interest, of which one objective is to manufacture a product that if recyclable by the paper industry and/or biodegradable.
For this purpose, the invention describes a process of the above-mentioned type, that is to say a manufacturing process using a soft material which is extruded under heat, encased in at least one strip sheet, and subsequently calendered, shaped to the desired profile and finally cut into lengths, but it is remarkable in that the matter used is a mixture containing a non-synthetic binder and water so that the mixture becomes sticky by undergoing said heat treatment in an aqueous medium, which ensures that the casing adheres to the matter during calendering while the product undergoes at least one drying operation after said calendering operation.
Not only does the invention give the benefit of all the advantages of biodegradable materials, but the choice of materials also assures simple, effective adhesion of the casing.
In fully advantageous manner, the non-synthetic binder contains starch which becomes sticky after gelling and fusion due to the heat treatment in an aqueous medium.
Generally, the starch-containing binder is derived from flour of non-foodstuff quality whose dry mass proportion in the mixture exiting the extruder is between 4 and 30%.
Preferably, the sheet or sheets intended to form the casing are chiefly made up of resistant paper or cardboard, and they may evidently be made up of a complex.
To assure good adhesion, the water content of the mixture exiting the extruder is, for example, between 4.5% and 15%.
According to one embodiment, the mixture comprises a plasticizer, contained for example in the mixture in a dry mass proportion of between 5% and 15%, said plasticizer containing a fatty acid or urea.
With a starch-based binder, the temperature of the material in the extruder is maintained between the melting point of starch, which depends upon its water content, and the degradation temperature of urea, this temperature being for example maintained for at least a certain time within a range of between 130xc2x0 C. and 150xc2x0 C. The temperature is adjusted in relation to the chosen water content.
Advantageously, the mixture also comprises biodegradable loads, the latter being for example contained in the mixture in a dry mass proportion of 40% to 85% and comprising mainly paper for example up to ⅘.
According to one embodiment, the product undergoes drying during processing, using for example infra-red and/or micro-wave and/or high frequency
However, and in addition, specific drying can be provided at the end of manufacture on each length of section or plate, which are passed in front of means blowing hot air.
According to one embodiment, at least one of the sheets intended to form the casing is permeable in order to facilitate drying of the finished or semi-finished product, said sheet being, for example, made permeable by perforation in numerous plates before depositing the matter.
The sheet or sheets intended to form the casing, may only partially surround the matter in order to facilitate drying of the finished or semi-finished product.
The invention also concerns an installation for implementing the process, said installation comprising extrusion means for soft matter, means for encasing the latter at least in part, and means for its calendering, forming and cutting into lengths, while it is remarkable in that it also comprises drying means placed between at least some of said processing means.
Said installation may also comprise a drying unit positioned after the length cutting means, said unti comprising means of blowing hot air and means of transporting section lengths. The installation may also comprise perforating means to perforate at least one of the sheets intended to form the casing according to one embodiment of the process of the invention as mentioned above.
Finally, the invention evidently relates to any section or plate formed from the soft matter encased by at least one sheet which is manufactured according to the above-mentioned process.